Lens for optical treatment

ABSTRACT

A method for treating progression of a refractive disorder in a human eye. The method includes the steps of producing a first image on a retina of the human eye and producing a second image to generate a defocus.

Notice: More than one reissue application has been filed of the reissueof U.S. Pat. No. 7,506,983. The reissue applications are applicationSer. No. 14/457,080, filed on Aug. 11, 2014 (the present application),application Ser. No. 13/662,420, filed on Oct. 27, 2012 (now U.S. Pat.No. RE45,147), and application Ser. No. 13/053,289, filed on Mar. 22,2011 (now U.S. Pat. No. RE43,851).

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation reissue application of applicationSer. No. 13/662,420, now RE45,147, which is a continuation reissueapplication of application Ser. No. 13/053,289, now RE43,851, which is areissue of U.S. Pat. No. 7,506,983.

FIELD OF THE INVENTION

The present invention relates to a method of optical treatment. Inparticular, the present invention relates to a method for treatingprogression of refractive disorders, such as myopia and hyperopia, inhuman eyes.

BACKGROUND OF THE INVENTION

The retina is the innermost layer of an eyeball and is the place whereoptical images created by the lens of the eye is focused. Theinformation from the images are turned into nerve impulses, which arethen sent to the brain via the optic nerve. If the retina does notcoincide with the resultant focal point of the optical elements of theeye, defocus is generated. As used herein, the term “defocus” refers tothe shift of the optical images to a point behind or in front of theretina. The human eye has a feedback mechanism that regulates the growthof the eye to achieve an optimal balance between the size/length of theeye and the focal length of the optical elements of the eye. Thisfeedback mechanism is called emmetropization.

Myopia and hyperopia are common refractive disorders of human eyes. Theyare generally described as an imbalance between the focusing power ofoptical elements of the eye and the size/length of the eye. Focus of amyopic eye lies in front of the retina of the eye, while focus of ahyperopic eye lies behind the retina of the eye. It is generallyaccepted that these disorders are results of inaccurate axial growthduring post-natal development of the eyes. In other words, myopiatypically develops when the size/length of the eye grows to exceed thefocal length of the optical elements of the eye, while hyperopiatypically develops when the size/length of the eye grows to be shorterthan the focal length of the optical elements of the eye.

Referring to FIG. 1, an optical image 12 is formed in front of theretina in the case of myopia. Defocus in this case is positive andcalled myopic defocus 13. The emmetropization mechanism operates toretard eye growth in size until the retina 11 coincides with the opticalimage 12 when the myopic defocus 13 diminished. As a result, the eyebecomes less myopic.

Referring to FIG. 2, optical image 22 is formed behind the retina 21 inthe case of hyperopia. Defocus in this form is negative and calledhyperopic defocus 23. The emmetropization mechanism operates to promoteeye growth in size until the retina 21 coincides with the optical image22 when the hyperopic defocus 23 diminished. As a result, the eyebecomes less hyperopic.

Referring to FIG. 3, the natural major sources of defocus for a humaneye come from accommodation lag and ambient defocus. The accommodationlag is generally projected by the object of interest 35 onto the centerof the retina 31 or macula 34 along a visual axis 32. It usually rangesfrom 0.5 D to 1.0 D of hyperopic defocus 36 for a non-presbyope duringnear visual tasks, such as reading. Ambient defocus is projected byperipheral visual objects other than the object of interest 35. Sinceperipheral objects are usually positioned more distant than the objectof interest 35, they usually produce myopic defocus up to 3.0 D duringnear visual tasks. For example, peripheral object 37 produce myopicdefocus 38 at periphery of retina 31. Habitually, the peripheral visualobjects are seldom positioned closer than the object of interest 35.However, if they do like peripheral object 39, hyperopic defocus 33 willbe produced.

The natural process of emmetropization is regulated by the equilibriumbetween the above opposite defocus. Incidences of refractive errors aresecondary to the disruption of the equilibrium. For example,insufficient ambient myopic defocus may cause myopia. On the other hand,excessive ambient myopic defocus may cause hyperopia.

Existing optical aids and refractive surgeries, in the form ofspectacles, contact lens, corneal implant or shape modification ofcornea, are corrective approaches involving alteration of the grossfocusing power of the eye to produce sharper retinal images. They do noteliminate or deal with the cause of the disorders, but are justprosthetic.

The existing optical treatments to retard the progression of myopia byrelieving the eye's accommodation during near visual tasks are recentlyshown to be clinically ineffective. Examples of those treatments includebi-focal addition lenses, multi-focal progressive addition lenses andtheir derivatives, and spherical aberration manipulations.

SUMMARY OF THE INVENTION

The present invention is directed to a method for treating progressionof a refractive disorder in a human eye. Particularly, the presentinvention provides methods for counteracting the development of myopiaby enhancing myopic defocus. The present invention also provides methodsfor counteracting the development of hyperopia by enhancing hyperopicdefocus. The apparatuses used in practice of the present invention alterthe defocus equilibrium of the eye to influence axial eye growth in adirection towards emmetropia.

According to a general aspect of the present invention, the method fortreating progression of a refractive disorder in a human eye includesproducing a first image on a retina of the human eye and producing asecond image to generate a defocus.

According to one aspect of the present invention, the method fortreating progression of a refractive disorder in a human eye includesproviding a Fresnel lens having primary optical zones and secondaryoptical zones. The primary optical zones include a primary refractivepower, and secondary optical zone includes at least one secondaryrefractive power. The method also includes correcting the refractivedisorder with the primary refractive power and generating at least onedefocus with the secondary refractive power.

According to another aspect of the present invention, the method fortreating progression of a refractive disorder in a human eye includesprescribing an optical system having a back layer and a partiallytransparent front layer. The method also includes producing a primaryimage of one of the front and back layers on a retina of the human eyeand producing a secondary image of the other layer of the front and backlayers to generate a defocus.

According to yet another aspect of the present invention, the method fortreating progression of a refractive disorder in a human eye includesproviding a lens including a central optical zone having a primaryoptical power and at least one peripheral optical zone having asecondary optical power. The method also includes producing a primaryimage on a retina of the human eye with the first optical power andproducing at least one secondary image with the second optical power togenerate a defocus.

According to yet another aspect of the present invention, the method fortreating progression of a refractive disorder in a human eye includesprescribing an optical system having a central visual object and atleast one peripheral visual object. The method also includes producing afirst image of the central visual object on a central retina of thehuman eye and producing a second image of the peripheral visual objectto generate a defocus.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing the section of a myopic eye andthe nature of myopic defocus.

FIG. 2 is a schematic diagram showing the section of a hyperopic eye andthe nature of hyperopic defocus.

FIG. 3 is schematic diagram showing the section of an eye, illustratingthe source and the formation of accommodation lag and ambient defocus.

FIG. 4a is a cross-sectional view of a Fresnel type concentric bi-focalor multi-focal lens used in practice of the present invention.

FIG. 4b is a back view of the Fresnel type concentric bi-focal ormulti-focal lens of FIG. 4a.

FIG. 5a is a diagram of a myopic eye fitted with a concentric bi-focallens in accordance with the present invention.

FIG. 5b is a diagram of a myopic eye fitted with a concentricmulti-focal lens in accordance with the present invention.

FIG. 6a is a diagram of a hyperopic eye fitted with a concentricbi-focal lens in accordance with the present invention.

FIG. 6b is a diagram of a hyperopic eye fitted with a concentricmulti-focal lens in accordance with the present invention.

FIG. 7a is a diagram of a myopic eye fitted with an optical systemhaving of a semi-transparent front layer and a non-transparent backlayer in accordance with the present invention.

FIG. 7b is a diagram of a hyperopic eye fitted with an optical systemhaving a non-transparent back layer and a semi-transparent front layerin accordance with the present invention.

FIG. 8a is a cross-sectional view of a central-peripheral multi-focallens used in practice of the present invention.

FIG. 8b is a back view of the central-peripheral multi-focal lens ofFIG. 8a.

FIG. 9 is a diagram of a myopic eye fitted with the central-peripheralmulti-focal lens of FIG. 8a and FIG. 8b in accordance with the presentinvention.

FIG. 10 is a diagram of a hyperopic eye fitted with thecentral-peripheral multi-focal lens of FIG. 8a and FIG. 8b in accordancewith the present invention.

FIG. 11a is a diagram of a myopic eye fitted with an optical systemhaving peripheral visual objects positioned closer than a central visualobject in accordance with the present invention.

FIG. 11b is a diagram of a hyperopic eye fitted with an optical systemhaving peripheral visual objects positioned closer than a central visualobject in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a method for treating progressionof a refractive disorder in a human eye. Particularly, the presentinvention provides a method for counteracting the development of myopiaby enhancing myopic defocus. The present invention also provides amethod for counteracting the development of hyperopia by enhancing ofhyperopic defocus. The apparatuses used in practice of the presentinvention alter the defocus equilibrium of the eye to influence axialeye growth in a direction towards emmetropia.

The artificial shift of the defocus equilibrium in the optical system ofthe eye may be introduced by any desired method, for example byspectacle lens, spectacle lens add-on, contact lens, cornealshape-modification, ocular implant or designated viewing system. It ispreferred that the shift be introduced together with the conventionalcorrection so that normal vision can be maintained throughout thetreatment. This means that a focused image must be maintained near themacula 34, while one or more defocused images are being introduced intothe optical system of the eye.

A treatment method in accordance with the present invention introducesat least a defocused image and a focused image in a superimposed manner.The defocused and focused images can be introduced simultaneously, forexample, by a concentric Fresnel type bi-focal or multi-focal lens asshown in FIGS. 4-6, diffractive multi-focal lens and their derivatives,or an optical system as shown in FIG. 7.

Referring now FIGS. 4a and 4b, there shown is the Fresnel concentricbi-focal or multi-focal lens having alternating concentric optic zones41 and 42 of at least two refractive powers used in practice of thepresent invention. A common way to manufacture the Fresnel concentricbi-focal lens is to make one of the surfaces with two radius ofcurvature. For example, the zone 42 with a shorter radius of curvature(i.e. more curved) than the other zone 41 with a longer radius ofcurvature (i.e. flatter) exhibits a more negative refractive power. Thezone with a more negative power 44 and the zone with a less negativepower 43 alternate in a concentric manner. As a result, paraxial lightrays and peripheral light rays share two common focal points.

FIG. 5a shows a myopic eye fitted with a Fresnel type concentricbi-focal lens 50 having a primary refractive power correcting the myopiaand a secondary power to introduce myopic defocus in accordance with thepresent invention. Light rays 51 entering the optical zones having theprimary power are focused on the retina 52, producing a sharp image of avisual object. At the same time, other light rays 53 entering theoptical zones having the secondary power are focused at a point 54 infront of the retina 52, producing the myopic defocus 55. When a myopicpatient uses the lens 50 to view an object, the myopic defocus 55prevents the eye from growing or elongating. Consequently, myopicprogression in the myopic eye is slowed, stopped or reversed.

FIG. 6a shows a hyperopic eye fitted with a Fresnel type concentricbi-focal lens 60 having a primary refractive power to correct thehyperopia and a secondary power to introduce hyperopic defocus. Lightrays 61 entering the optical zones having the primary power are focusedonto the retina 62, producing a sharp image of a visual object.Simultaneously, other light rays 63 entering the optical zones havingthe secondary power are focused at a point 64 behind the retina 62,producing the hyperopic defocus 65. When a hyperopic patient uses thelens 60 to view an object, the hyperopic defocus 65 promotes the eye ingrowing or elongating. Consequently, myopic progression in the hyperopiceye is increased or induced, and hyperopia is reduced.

A Fresnel type of concentric multi-focal lens is a derivative of theFresnel type concentric bi-focal lens. It has alternating concentricoptic zones of more than two refractive powers. The primary refractivepower corrects the refractive error, while the multiple secondary powersintroduce optical defocus for treatment. This can be achieved by a minorvariation on the radius of curvature of the secondary optical zones.

FIG. 5b shows a myopic eye fitted with a Fresnel type concentricmulti-focal lens 56 in accordance with the present invention. Light rays51 entering the optical zones having the primary power are focused onthe retina 52, producing a sharp image of a visual object. At the sametime, other light rays 53 entering the optical zones having thesecondary powers are focused at points 57 in front of the retina 52,producing multiple myopic defocus 58 of various amplitudes. When amyopic patient uses the lens 56 to view an object, the myopic defocus 58prevent the eye from growing or elongating. Consequently, myopicprogression in the myopic eye is slowed, stopped or reversed.

FIG. 6b shows a hyperopic eye fitted with a Fresnel type concentricmulti-focal lens 66. Light rays 61 entering the optical zones having theprimary power are focused onto the retina 62, producing a sharp image ofa visual object. Simultaneously, other light rays 63 entering theoptical zones having the secondary powers are focused at points 67behind the retina 62, producing multiple hyperopic defocus 68 of variousamplitudes. When a hyperopic patient uses the lens 66 to view an object,the hyperopic defocus 68 promotes the eye in growing or elongating.Consequently, myopic progression in the hyperopic eye is increased orinduced, and hyperopia is reduced.

FIG. 7a shows a myopic eye fitted with an optical system having aprimary semi-transparent front layer 71 and a secondary non-transparentback layer 73 in accordance with the present invention. The front layer71 matches the focal point of the eye, producing a sharp image 72 on theretina. At the same time, the back layer 73 produces an image 74 infront of the retina causing a myopic defocus 75 superimposed on thesharp image 72. When a myopic patient uses this optical system, themyopic defocus 75 prevents the eye from growing or elongating.Consequently, myopic progression in the myopic eye is slowed, stopped orreversed.

FIG. 7b shows a hyperopic eye fitted with an optical system having aprimary non-transparent back layer 76 and a secondary semi-transparentfront layer 78 in accordance with the present invention. The back layer76 matches the focal point of the eye, producing a sharp image 77. Inthe same time, the front layer 78 produces an image 79 behind the retinacausing a hyperopic defocus 80 superimposed on the sharp image 77. Whena hyperopic patient uses this optical system, the hyperopic defocus 80promotes the eye in growing or elongating. Consequently, myopicprogression in the hyperopic eye is increased or induced, and hyperopiais reduced.

To improve the visual performance produced by the treatment methods andto avoid the user from mixing up his or her primary and secondaryoptical components, the optical quality of the retinal image produced bythe primary components can be strengthened over the image produced bythe secondary components. This can be achieved by manipulating the arearatio between the different zones of the Fresnel lenses and manipulatingthe transmission proportion of the semi-transparent layers.

An alternative method in accordance with the present inventionintroduces defocused image at peripheral retina only and keeps focusedimage at central retina. People habitually maintain a sharp image atcentral retina by a voluntary fixation reflex. Accordingly, the way tosimultaneously present two images is the introduction of the defocusimage at peripheral retina through the use of a central-peripheralmulti-focal lens as shown in FIGS. 8-10 and a optical system as shown inFIG. 11.

As shown in FIGS. 8a and 8b, the central-peripheral multi-focal lensincludes concentric optical zones of two or more optical powers. One wayto manufacture this kind of lens is to generate the zones with materialsof different refractive index. The central zone 81, which has a higherrefractive index than the peripheral zone 82, exhibits higher refractivepower. The two zones 81 and 82 are positioned in a generally concentricmanner, with the refractive power decreasing from the central towardsthe peripheral across the lens. The transition can be subtle orprogressive, depending on the manufacturing process.

FIG. 9 shows a myopic eye fitted with a negative central-peripheralmulti-focal lens, which has a primary central refractive powercorrecting the myopia and a secondary peripheral refractive power tointroduce myopic defocus, in accordance with the present invention.Light rays entering the central zone of the lens from a central visualobjects 91 are focused onto the central retina, producing acorresponding central sharp image 92. Simultaneously, light raysentering the peripheral zone of the lens from the peripheral visualobjects 93 are focused at points in front of the peripheral retina,producing the peripheral myopic defocus 94 required for the treatmenteffect for myopia. When a myopic patient uses the lens to view thevisual objects 91 and 93, the myopic defocus 94 prevents the eye fromgrowing or elongating. Consequently, myopic progression in the myopiceye is slowed, stopped or reversed.

FIG. 10 shows a hyperopic eye fitted with a positive central-peripheralmulti-focal lens, which have a primary central refractive powercorrecting the hyperopia and a secondary peripheral refractive power tointroduce hyperopic defocus, in accordance with the present invention.Light rays entering the central zone of the lens from the central visualobjects 101 are focused onto the central retina, producing acorresponding central sharp image 102. Simultaneously, light raysentering the peripheral zone of the lens from the peripheral visualobjects 103 are focused at points behind the peripheral retina,producing the peripheral hyperopic defocus 104 required for thetreatment effect for hyperopia. When a hyperopic patient uses thisoptical system, the hyperopic defocus 104 promotes the eye in growing orelongating. Consequently, myopic progression in the hyperopic eye isincreased or induced, and hyperopia is reduced.

FIG. 11a shows a myopic eye fitted with a pre-designed visualenvironment or an optical system, which has peripheral visual objects113 positioned far away from the eye compared with the central visualobject 111, in accordance with the present invention. Light rays fromthe central object 111, as directed by basic optics and the fixationreflex of the eye, are focused onto the central retina, producing acorresponding central sharp image 112. Simultaneously, light rays fromperipheral visual objects 113 are focused at points in front of theperipheral retina, producing peripheral myopic defocus 114 required forthe treatment of myopia. When a myopic patient uses this optical system,the myopic defocus 114 prevents the eye from growing or elongating.Consequently, myopic progression in the myopic eye is slowed, stopped orreversed.

FIG. 11b shows a hyperopic eye fitted with a pre-designed visualenvironment or an optical system, which has peripheral visual objects117 positioned close to the eye compared with the central visual object115. Light rays from the central object 115, as directed by basic opticsand the fixation reflex of the eye, are focused onto the central retinaproducing a corresponding central sharp image 116. Simultaneously, lightrays from peripheral visual objects 117 are focused at points behind theperipheral retina, producing peripheral hyperopic defocus 118 requiredfor the treatment of hyperopia. When a hyperopic patient uses thisoptical system, the hyperopic defocus 118 promotes the eye in growing orelongating. Consequently, myopic progression in the hyperopic eye isincreased or induced, and hyperopia is reduced.

Although the present invention has particular applications in curing andpreventing the progression of refractive disorders of the eye such asmyopia and hyperopia, it is to be understood that the invention could beused in other applications such as the prevention of pathological myopicdegeneration of the eye.

Although the present invention has been described with reference topreferred methods, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention. In addition, the invention is not to betaken as limited to all of the details thereof as modifications andvariations thereof may be made without departing from the spirit orscope of the invention.

We claim:
 1. A method for retarding the progression of myopia orhyperopia in a human eye, the method comprising: (a) providing a Fresnelconcentric multi-focal lens comprising primary optical zones having aprimary refractive power and secondary optical zones having at least onesecondary refractive power; and (b) correcting the myopia or hyperopiawith the primary refractive power and generating at least one defocuswith the secondary refractive power, wherein the primary optical zonesenable near and distant objects to be viewed; and the secondary opticalzones generate myopic defocus to retard myopia or generate hyperopicdefocus to retard hyperopia.
 2. The method of claim 1, wherein: the step(b) comprises focusing a first stream of light rays of an object onto aretina of the human eye through the primary optical zones to correct themyopia and focusing a second stream of light rays of the object in frontof the retina through the secondary optical zones to generate at leastone myopic defocus.
 3. The method of claim 1, wherein: the step (b)comprises focusing a primary stream of light rays of an object onto aretina of the human eye through the first optical zones to correct thehyperopia and focusing a second stream of light rays of the objectbehind the retina through the secondary optical zones to generate atleast one hyperopic defocus.
 4. The method of claim 1, wherein the step(a) comprises prescribing a Fresnel concentric bi-focal lens to producea defocus in step (b).
 5. The method of claim 1, wherein the step (a)comprises providing a Fresnel concentric multi-focal lens producing twoor more defocuses in step (b).
 6. The method of claim 1, wherein theFresnel concentric multi-focal lens is a concentric bi-focal lens.
 7. Aconcentric multi-focus lens for retarding the progression of myopia in ahuman eye, the lens comprising: a first lens side; a primary opticalzone on the first lens side having a first curvature configured to forma primary refractive power, wherein the primary refractive power isconfigured to correct the myopia; and a secondary optical zone on thefirst lens side having at least one second curvature configured to format least one secondary refractive power, the at least one secondcurvature being different and non-continuous relative to the firstcurvature, wherein the secondary refractive power is configured togenerate at least one myopic defocus to retard myopia.
 8. The lens ofclaim 7, the primary optical zone is configured to focus a first streamof light rays of an object onto a retina of the human eye to correct themyopia, and the secondary optical zone is configured to focus a secondstream of light rays of the object in front of the retina to generate atleast one myopic defocus.
 9. The lens of claim 7, wherein the lens is abi-focal lens configured to produce a single defocus to retard myopia.10. The lens of claim 7 comprising a third optical zone having a thirdrefractive power configured to generate another myopic defocus to retardmyopia.
 11. The lens of claim 7, wherein the lens is configured toproduce two or more defocuses to retard myopia.
 12. The lens of claim 7,wherein the primary optical zone is configured to generate a focusedimage in a central optic zone, and the secondary optical zone isconfigured to generate a defocused image in the central optic zone at aspaced distance from the focused image.
 13. The lens of claim 7, whereinthe lens is a contact lens.
 14. The lens of claim 7, wherein thetransition between the primary optical zone and the secondary opticalzone is progressive.
 15. A lens for retarding the progression of myopiain a human eye, the lens comprising: a first lens side; a primaryoptical zone on the first lens side having a first curvature configuredto form a primary refractive power, wherein the primary refractive poweris configured to correct the myopia during usage of the lens; and asecondary optical zone on the first lens side having at least one secondcurvature configured to form at least one secondary refractive power,wherein the at least one second curvature is different andnon-continuous relative to the first curvature, wherein the secondaryrefractive power is configured to generate at least one myopic defocusto retard myopia during usage of the lens, and wherein at least part ofthe secondary optical zone is formed concentrically about at least partof the primary optical zone.
 16. The lens of claim 15, wherein duringuse for retarding the progression of myopia, the primary optical zone isconfigured to focus a first stream of light rays of an object onto aretina of the human eye to correct the myopia, and the secondary opticalzone is configured to focus a second stream of light rays of the objectin front of the retina to generate at least one myopic defocus.
 17. Thelens of claim 15, wherein the lens is a bi-focal lens configured toproduce a single defocus to retard myopia.
 18. The lens of claim 15comprising a third optical zone having a third refractive powerconfigured to generate another myopic defocus to retard myopia, whereinat least part of the third optical zone is formed concentrically aboutat least part of the secondary optical zone.
 19. The lens of claim 15,wherein the lens is configured to produce two or more defocuses toretard myopia.
 20. The lens of claim 15, wherein the primary opticalzone is configured to generate a focused image in a central optic zone,and the secondary optical zone is configured to generate a defocusedimage in the central optic zone at a spaced distance from the focusedimage.
 21. The lens of claim 15, wherein the lens is a contact lens. 22.The lens of claim 15, wherein the transition between the primary opticalzone and the secondary optical zone is progressive.
 23. A concentricmulti-focus contact lens for retarding the progression of myopia in ahuman eye, the lens comprising: a first lens side; a centrally locatedprimary optical zone on the first lens side having a first curvatureconfigured to form a primary refractive power, wherein the primaryrefractive power is configured to correct myopia by generating a focusedimage in a central optic zone of the human eye during usage of the lens;and a secondary optical zone on the first lens side having at least onesecond curvature configured to form at least one secondary refractivepower, wherein the at least one second curvature is different andnon-continuous relative to the first curvature, wherein at least part ofthe second optical zone is concentrically located about at least part ofthe centrally located primary optical zone, and wherein the secondaryrefractive power is configured to generate at least one defocused imagein the central optic zone of the human eye at a spaced distance from thefocused image during usage of the lens to retard myopia.
 24. The lens ofclaim 23, wherein the transition between the primary optical zone andthe secondary optical zone is progressive.